This invention relates to a method for controlling a piston-type internal-combustion engine in which each cylinder is provided with at least two intake valves which, for each cylinder, are coupled to one another by a common intake port into which fuel is introduced by means of at least one fuel injection nozzle and wherein only a single intake valve per stroke is operated in the lower load range.
Piston-type internal-combustion engines having electromagnetic actuators for operating the cylinder valves provide the possibility for a fully variable control of the cylinder valves, wherein in particular the opening and closing moments of the valves as well as the "open" periods of the valves may be determined practically at will. In such engines which thus have at least two intake valves, it is feasible to maintain one of the intake valves closed (inoperative) in the lower load range, so that the entire operation is performed solely by actuating the other intake valve. In such engines the two intake valves are in communication with one another by a common "Siamese" intake port, into which the fuel is introduced by means of at least one fuel injection nozzle. If in the lower load range one of the intake valves is maintained closed so that the entire operation is effected by operating the other valve, in front of the closed valve fuel accumulates which does not gain access to the combustion chamber. Such a circumstance leads to an improper setting of the X-regulation. If now, based on load requirements, the other, heretofore closed intake valve is again rendered operative by means of the control device, the accumulated fuel gains access to the combustion chamber, disadvantageously resulting in an undefined mixture formation. Such an undesired enrichment of the mixture leads to a poor combustion. In case of a long operational period in a single-valve mode, it may even occur that the sudden introduction of the accumulated fuel leads to a mixture which is no longer ignitable. Also, due to the poor combustion, the exhaust gas is high in hydrocarbon pollutants. The exhaust gas values significantly worsen due to the undesired, incorrect mixture formation.